Brazilian Journal of Medical and Biological Research (2001) 34: 871-877 Heart rate variability in postmenopausal and young women ISSN 0100-879X 871 Heart rate variability under resting conditions in postmenopausal and young women T.F. Ribeiro 1,4, G.D. Azevedo 5, J.C. Crescêncio 4, V.R.F.S. Marães 1, V. Papa 1, A.M. Catai 1, R.M.M. Verzola 2, L. Oliveira 3, M.F. Silva de Sá 5, L. Gallo Jr. 4 and E. Silva 1 1 Laboratório de Fisioterapia Cardiovascular, Departamento de Fisioterapia, 2 Departamento de Ciências Fisiológicas and 3 Departamento de Física, Universidade Federal de São Carlos, São Carlos, SP, Brasil 4 Divisão de Cardiologia, Departamento de Clínica Médica, and 5 Departamento de Ginecologia e Obstetrícia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil Correspondence E. da Silva Laboratório de Fisioterapia Cardiovascular Departamento de Fisioterapia, UFSCar Rodovia Washington Luís, km 235 13565-905 São Carlos, SP Brasil E-mail: esters@power.ufscar.br Research supported by CAPES, CNPq (Nos. 300528/85 and 520686/95) and FAPESP (No. 98/13257-8). Received May 15, 2000 Accepted March 2, 2001 Abstract Key words Heart rate variability Menopause Autonomic nervous system Time domain indexes Introduction
872 T.F. Ribeiro et al. Methods
Heart rate variability in postmenopausal and young women 873 Results R-R interval (ms) 1250 1150 1050 950 850 750 650 0 60 120 180 240 300 360 Time (s) Figure 1. R-R interval, in ms, for the young (gray) and postmenopausal (black) volunteers under resting conditions in the supine position (N = 2). 1250 RMSM = å N 2 RR - RR ( i ) i= 1 N 1150 1050 RMSSD = å N-1 2 ( RRi - RRi+ 1) i= 1 N-1 R-R interval (ms) 950 850 750 650 0 60 120 180 240 300 360 Time (s) Figure 2. R-R interval, in ms, for the young (gray) and postmenopausal (black) volunteers under resting conditions in the sitting position (N = 2).
874 T.F. Ribeiro et al. Table 1. Anthropometric, clinical and hormonal characteristics of the groups studied. Characteristic Age (years) 21.6 ± 0.82 58.3 ± 6.8** Height (cm) 161.6 ± 4.74 156.3 ± 5.51* Weight (kg) 56.3 ± 6.62 65.2 ± 12.11* Body mass index (kg/m 2 ) 21.4 ± 1.43 23.2 ± 6.42 Systolic blood pressure (mmhg) 108.2 ± 8.45 124.6 ± 14.6** Diastolic blood pressure (mmhg) 71.4 ± 7.44 78.5 ± 9.07* Follicle-stimulating hormone level (miu/ml) 4.8 ± 0.78 79.1 ± 35.54** Luteinizing hormone level (miu/ml) 3.1 ± 0.76 22.1 ± 10.66** Prolactin level (ng/ml) 11.6 ± 5.48 4.5 ± 1.71** Serum estradiol level (pg/ml) 43.7 ± 8.23 <20 a * Values are reported as means ± SD. a Lower concentration of assay standard curve. N = 10 for each group. * and **P<0.001 compared to young volunteers (Mann- Whitney test). Figure 3. RMSM indexes, the standard deviation of R-R intervals, in ms, for the young group (N = 10) and the postmenopausal group (N = 10) under resting conditions in the supine and sitting positions. Figure 4. RMSSD indexes, the square root of the mean of the squared differences between adjacent normal R-R intervals, in ms, for the young group (N = 10) and the postmenopausal group (N = 10) under resting conditions in the supine and sitting positions. RMSM of R-R intervals (ms) RMSSD of R-R intervals (ms) 120 100 80 60 40 20 0 Non-outlier max Non-outlier min 120 100 80 60 40 20 0 75% 25% Median Outliers Non-outlier max Non-outlier min 75% 25% Median Outliers Extremes Discussion
Heart rate variability in postmenopausal and young women 875 Heart rate (bpm) 95 90 85 80 75 70 65 60 55 50 P = 0.024 Non-outlier max Non-outlier min P = 0.3150 P = 0.2701 P = 0.30 75% 25% Median Outliers Figure 5. Mean heart rate, in bpm over a period of 6 min for the young group (N = 10) and the postmenopausal group (N = 10) under resting conditions in the supine and sitting positions.
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